Evaporative emissions control systems capture fuel vapors in a charcoal canister, e.g., when a vehicle is parked, then burn the vapors in the engine when it is running. In some approaches a vacuum generated in the engine's intake manifold is used to pull air through the charcoal canister in order to purge the fuel therein. In some examples, such fuel vapor purging systems may be employed in engines which include features to increase fuel economy, e.g., via variable camshaft timing, variable valve lift, engine downsizing, e.g. EcoBoost, hybridization, e.g., in a hybrid electric vehicle (HEV), etc.
However, such approaches which increase fuel economy may reduce an amount of vacuum in the intake manifold, and/or how often vacuum is available, thus reducing an amount of vacuum available to purge fuel vapors from a fuel vapor purge system. Further, in some examples, if more purge vacuum is desired in such approaches, fuel economy may be sacrificed in order to increase vacuum for fuel purging, e.g. by forcing an engine re-start on an HEV or by reducing use of variable camshaft timing or variable valve lift. Some approaches may employ electric pumps for vapor purge in order to avoid this fuel economy penalty. However, such pumps may be expensive, and the electricity to power them may increase parasitic loads which degrade fuel economy.
In some approaches, a venturi or aspirator may be coupled in an intake system of the engine and a fuel vapor purge system, or other systems which require vacuum, may be coupled to an inlet of the venturi so that vacuum generated in the venturi may be provided to the fuel vapor purge system, or other vacuum system. However, the inventors have recognized issues with such approaches. For example, a venturi coupled in an intake system of an engine may restrict flow so that wide-open throttle performance may be degraded. Further, in such approaches, the position of the venturi relative to a throttle may degrade engine performance. For example, if a venturi is disposed in an intake system downstream of a throttle, the air volume downstream of the throttle may be increased, which may lead to a degraded transient torque response, especially in turbocharged engines. As another example, if a venturi is disposed in an intake system upstream of a throttle, an increase in throttle body deposits may occur in the throttle when a fuel vapor purging system is coupled to an inlet of the venturi.
In order to at least partially address these issues, systems and methods for an operating engine comprising a venturi coupled in an intake system of the engine are provided. In one example approach, a method of controlling operation of an engine having a fuel vapor purging system comprises: directing intake air through a first throttle and a venturi disposed in a bypass conduit coupled to an intake system of the engine upstream and downstream of a second throttle disposed in the intake system; and in response to an operating condition, delivering fuel vapor flow from the fuel vapor purging system to an inlet of the venturi.
In this way, the venturi or aspirator in the intake manifold may be employed to increase an amount and availability of vacuum for fuel vapor purging which may reduce component costs and increase fuel economy while providing sufficient vacuum to the vapor purging system while reducing impact on wide open throttle performance, for example.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.